Monomorphic adenoma is a rare benign salivary gland epithelial tumor representing <3% of all tumors in general population, and more than 80% of them arise in the major salivary glands, mostly the parotid gland and rarely in upper lip, buccal mucosa - as observed in the present case. Monomorphic adenomas are defined as epithelial benign tumors of the salivary glands, which are not pleomorphic adenomas. Due to prognostic implications, differential diagnosis (adenocarcinoma, adenoid cystic carcinoma, basaloid squamous cell carcinoma, mucocele, sebaceous cyst, lipoma, nasolabial cyst, etc.,) is mandatory. The present case report describes a rare case of monomorphic adenoma involving minor salivary glands with added review the literature; discuss the diagnosis and management of this rare entity and special emphasis on the need for periodic follow-up, due to the important relapse potential and aggressivity of these lesions.

A salivary gland neoplasms represents <1% of all tumors, and 3-5% of all head and neck tumors. Minor salivary gland tumors are infrequent, accounting for 10-15% of all salivary gland neoplasm's and are fundamentally located in the:

Monomorphic is an uncommon benign epithelial tumor of the salivary gland, accounting for 1-2% of all salivary gland tumors. [3] Classifications of salivary gland monomorphic adenomas use a variety of principles, including the type of cell, cellular arrangement, and embryologic development, and as a result, could represent a heterogeneous group of tumors.

Within the adenomas group, monomorphic tumors are very uncommon. Frequently, this slow growing encapsulated tumor does not exceed 3 cm of major diameter. It is a firm, mobile painless mass, usually superficial within the glandular body, and a brownish appearance is usually observed. [5] Globally, as it has been referred in classic texts, the tumor adopts an ameloblastoma like pattern (as evidenced in the present histopathological case report). [6]

Clinical appearance of monomorphic adenoma may stimulate mucocele of the oral mucosa. In general, the latter usually appears in the lower lip of young people, whereas the former usually appears in the upper lip of the elder. [7]

Case Report

A 55-year-old male patient reported to Tatyasaheb Kore Dental College and Research Institute, Department of Oral and Maxillofacial Surgery with 2 years slow growing tumor in the region of the right buccal mucosa. Physical examination revealed a mass measuring 1.5 cm × 1.5 cm, which was soft, freely movable and nontender mass at the cheek mucosa in relation to 15.16 region [Figure 1] and [Figure 2].

Lymph node examination was noncontributory in the cervical and facial region. Upon aspiration, negative pressure was observed suggestive of solid lesion. With the suspected diagnosis of benign salivary gland tumor (based in clinical findings), surgical removal of the tumor with safety margins was performed under local anesthesia with conscious sedation [Figure 3] and [Figure 4]. The histopathological study was monomorphic adenoma of minor salivary gland [Figure 5]. No important complications during the immediate postsurgical phase were observed.

The minor salivary glands consist of 600-1000 small independent glands found across the oral cavity, palatine tonsils, pharynx, and larynx. [8] The salivary gland neoplasms are rare and represent a variable group of benign and malignant tumors with different behavioral characteristics. The concept of salivary gland tumor exeresis was ascribed to BERTRANDI in 1802. [9]

Classification

According to Batsakis and Brannon [10] histological classification of monomorphic adenoma is as follows:

They appear as slow growing asymptomatic masses. They are an important issue in the science of head and neck pathology, due to their difficult diagnosis, management, and unpredictable clinical course of the disease. The minor salivary glands were the second common site of involvement, engaged in 28.5% of all tumors. [13] The management of monomorphic adenomas of the minor salivary glands is best treated by wide surgical excision including a margin of normal tissue, the extent of which will vary with tumor location, size, and histology.

The prognosis is favorable after wide excision. Periodic follow-up pattern is mandatory as the rate of malignant transformation and relapse is noted in the review of the literature. In the present case, report the patient was followed up at regular intervals (1, 3, and 6 months, 1-year postoperatively) to assess for the postoperative healing, recurrence.

The patient had no relapse or recurrence in the postoperative phase.

Conclusion

Minor salivary gland tumors are rare neoplasms. Nevertheless, a significant number of minor salivary gland tumors are asymptomatic and are picked up on routine dental examination; treatment should aim at complete excision of the tumor and allowing secondary healing of the lesion.

Irradiation is reserved for recurrences and inoperable cases. Patients with nonresectable tumors should receive radiation therapy although salivary gland tumors, as a group, are not highly radiosensitive. Chemotherapy is never curative, and its use as an adjunctive has not yet been established.

Despite this benign behavior, we think that it is completely necessary a long-term follow-up, in order to detect recurrences in prompt time.